1. Field of the Invention
The present invention relates to structural panels used to fabricate building walls, roofs and/or floors. More particularly, this invention relates to a light-weight building panel core of the type comprising in outer lattice, and inner lattice and a light-weight filler between the lattices. At the building installation site, a cementitious layer may be added to each side of the filler layer to enclose the respective lattice.
2. Description of the Background
Much effort has been expended for decades and considerable advancements have been made to reduce building costs. This effort has lead to increased use of fully prefabricated building panels throughout the world, which are shipped to the construction site then assembled to form building walls, roofs or floors. A substantially disadvantage of this technique is the expense of transportation, especially when the construction site is remote from the panel manufacturing plant. Accordingly, increased emphasis has recently been placed on building panel cores, which are substantially light-weight and thus have low shipping cost. The cores are shipped to the construction site, the panels are then interlocked to form the desired configuration for walls, ceilings or floors for the building, and the cementitious layer is then applied to the cores to form the completed panels.
Building panel cores are generally of three types. U.S. Pat. Nos. 4,226,067 and 4,340,802 disclose a structural panel which comprises an outer lattice, an inner lattice, and sinuous rods which interconnect the lattices. Each of the rods lie within a substantially single plane, so that the spacing between the lattices and between adjacent sinuous rods may be filled with elongate strips of light-weight filler material. The filler material may comprise polystyrene or urethane foam materials, and the strips are slid in place between the lattice and the sinuous rods to form the cores, which typically comprise 4' by 8' panels.
A second type of building core is commonly referred to as a foamed-in-place panel. This type of building core utilizes similar inner and outer lattices and interconnecting rods, although the rods which connect the lattices need not each lie within a single plane since the filler material is first formed in its desired final position between the inner and outer lattices. A significant disadvantage of this type of panel is the high cost of the equipment required to uniformly form the filler material in place between the lattices.
A third type of building core utilizes a conventional sheet of filler material, and the lattice layers are then positioned on each side of the sheet. The interior lattice is interconnected with the exterior lattice by a plurality of straight rods or wires which pierce through the filler material. The ends of the rods are welded or otherwise attached to the inner and outer lattice structures to complete the core. Because this latter technique utilizes low cost planar sheets of foam for the filler material rather than individual strips, and expensive formed in place machinery is not required, it is often the preferred type of building core.
One of the significant limitations to increase use of building cores to reduce construction cost is the somewhat justified concern that these panels will not withstand high forces of the type which are transmitted to the building in high winds, earthquakes, etc. The present invention is directed to providing improved building panels, and to improved building panel cores which overcome the limitations of prior art panels. In particular, the structural panels of the present invention have low manufacturing cost yet increase the ability of the panels to reliably withstand external forces.